A well-established power distribution system exists throughout most of the United States and other countries. The power distribution system provides power to customers via power lines. With some modification, the infrastructure of the existing power distribution system can be used to provide data communication in addition to power delivery. That is, data signals can be carried by the existing power lines that already have been run to many homes and offices. The use of the existing power lines may help reduce the cost of implementing a data communication system. To implement the data communication system, data signals are communicated to and from the power line at various points in the power distribution system, such as, for example, near homes, offices, Internet service providers, and like.
While the concept may sound simple, there are many challenges to overcome before using power lines for data communication. For example, a sufficient signal-to-noise ratio should be maintained, a sufficient data transfer rate should be maintained (e.g., 10 Mbps), “add on” devices should be installable without significantly disrupting power supply to power customers, “add on” devices should be designed to withstand outdoor conditions, bi-directional data communication should be supported, data communication system customers should be protected from the voltages present on power lines, and the like.
Power system transformers are one obstacle to using power distribution lines for data communication. Transformers convert voltages between power distribution system portions. For example, a power distribution system may include a high voltage portion, a medium voltage portion, and a low voltage portion and a transformers converts the voltages between these portions. Transformers, however, act as a low-pass filter, passing low frequency signals (e.g., 50 or 60 Hz power signals) and impeding high frequency signals (e.g., frequencies typically used for data communication) from passing through the transformer. As such, a data communication system using power lines for data transmission faces a challenge in passing the data signals from the power lines a to customer premise.
Moreover, accessing data signals on a power lines is a potential safety concern. Medium voltage power lines can operate from about 1000 V to about 100 kV which can generate high current flows. As such, any electrical coupling to a medium voltage power line is a concern. Therefore, a need exists for a device that can safely communicate data signals with a medium voltage power line and yet provide electrical isolation from the medium voltage power line.
In addition to communicating a data signal with a medium voltage power line, it would be advantageous to communicate the data signal to a low voltage power line for data distribution to a customer premise. That is, a need also exists for a device that electrically communicates a data signal between a medium voltage power line and a low voltage power line, while maintaining electrical isolation between the medium voltage power line and the low voltage power line.